US2880920A - Extension ladder - Google Patents

Description

April 7, 1959 L.'S. GLESSNER EXTENSION LADDER FiledAp-ril so, 1958 1 m a m m w m s C Q MQ VN m b 1 s 8 R 5 "w E 5 a E 35 M .m 5 L April 1959 L s. GLESSNER EXTENSION LADDER 5 Sheets-Sheet 2 Filed April 30, 1958 INVENTOR A55 5. GLESSNEQ ATTORNEYS April 7, 1959 L. s. GLESSNER 2,880,920

I EXTENSION LADDER Filed April 50, 1958 3 Sheets-Sheet 3 INVENTOR 55 5. GLESSNEE.

fllma, MW hm) ATTORNEYS United States Patent EXTENSION LADDER Lee S. Glessner, Wheeling, W. Va.

Application April 30, 1958, Serial No. 731,905

9 Claims. (Cl. 228-21) This invention relates to a screw actuated extensible stepladder.

While it has heretofore been known to actuate extensible ladders by screw mechanisms, such mechanisms have not heretofore been applicable to use in stepladders of the type here involved, wherein the ladder is supported by an angularly disposed prop member, the two being pivotally connected at their upper ends for relative angular folding movement. The production of an extensible stepladder of this type obviously involves the overcoming of several diflicult problems. For instance, in order to maintain equilibrium of the ladder, it is essential that both the ladder and its prop member be extended equally and simultaneously, so that suitable mechanisms must be associated with both the ladder and its said prop, and operated in coordinated relation. Moreover, the mechanism, in its entirety, must be so arranged that it will remain operable during the relative angular movement of the members that will occur as an inherent incident of their extension or retraction. The mechanism preferably should not interfere with the folding of the prop member against the ladder, as for transport.

Additionally, it will be desirable to link together the lower ends of the ladder member and its prop member to prevent inadvertent spreading of these lower ends with consequent collapse of the ladder while in use. This, too, is complicated by the necessity for avoiding interference by the connecting link with the aforementioned angular movement between the ladder and the prop incident to their extension. The present invention has been conceived with the foregoing problems in mind changing angular relationship between the nierhbers.

This will be readily permitted by the mechanism aforementioned.

It will be further apparent that a drive may be imp'arted to the threaded jack scfews through any one of said screws whereby said drive will be transmitted by the said pivot shaft to the other said screws.

Moreover, it will be readily apparent that by the application of a suitable hand crank or other actuating means to the said pivot shaft, a workman, while standing on the upper portion of the ladder, may readily adjust its height without necessity for descending the ladder.

In order to permit the aforementioned angular movement between the ladder members while maintaining their lower ends against spreading and in fixedly spaced relationship, I provide a link pivotally connected between the lower ends of the said members. Moreover, and as a further improvement on this particular feature, the lower ends of the respective members may be provided with ground engaging feet pivotally connected to the lower ends of the members coincidentally with the pivotal connections of said link.

The invention, in the presently preferred form, is illustrated in the accompanying drawings, in which 7 Fig. 1 represents a side elevation of a stepladder in accordance with the invention with the ladder in parand includes a novel arrangement of parts which successfully overcomes all of the foregoing obstacles in a novel, eflicient and simple manner.

To this end the invention broadly comprises the provision of the ladder and its prop in the form of a pair of individually extensible bipartite members, each comprising upper and lower slidably interconnected sections. The upper sections of these members are pivotally interconnected for angular movement about a common rotatable pivot shaft which is connected through suitable gearing with jack screws on the respective members, the screws extending radially to the said shaft and so geared thereto as to be swingable therearound without interfering with the geared connection between the shaft and each of said screws. Each jack screw is rotatably journalled and axially fixed on the upper section of its respective member and has a threaded connection with means fixed on the lower relatively slidably interconnected section of its respective member. Accordingly, rotation of either said screw will transmit equal simultaneous rotation to the other said screw or screws with resultant simultaneous extension or retraction of their respective members.

It will be apparent that such simultaneous extension or contraction of the pivotally interconnected members of the ladder while their lower ends are in fixedly spaced ground engaging relation, will result in a progressively tially raised or extended position;

Fig. 2 is a cross section on the line 2-2 of Fig. 1;

Fig. 3 is a view similar to Fig. 1 but with the ladder in its fully lowered or retracted position;

Fig. 4 is a cross section on the line 4-4 of Fig. 3;

Fig. 5 is a side elevation of the ladder as it appears when in folded condition ready for transport;

Fig. 6 is a fragmentary side elevation of one of the jack screw assemblies; and

Fig. 7 is a sectional view on the line 7--7 of Fig. 6. Referring now in detail to the accompanying drawings, the ladder comprises a pair of individually extensible bipartite members, including the ladder member designated 11 in its entirety and a prop member designated 12 in its entirety. The bipartite ladder member 11 comprises upper and lower slidably interconnected sections 11a and 11b and the prop member similarly comprises upper and lower slidably interconnected sections 12a and 12b. It will be seen that the two sections 11a and 11b of the ladder member are both provided with usual vertically spaced rungs 13 and the upper end of the ladder, in accordance with more or less usual practice, terminates in a rigidly attached step or platform 16.

Referring particularly to Fig. 4, it will be seen that the lower section 11b of the ladder comprises vertical side rails 17 extending parallel to each other in-a common plane, together with channelled guides 1818 in a plane'parallel and rigidly connected to rails 17. The guides 1818 slidably receive the vertical side rails 19 of the upper ladder section 11a.

The prop member 12 comprises simply the parallel channelled guides 12b of the lower section for sliding reception of the side rails 12a of the upper section, the ladder side rails being interconnected in parallel relationship by suitably disposed cross braces 21.

For the purpose of pivotally interconnecting the upper ends of the two extensible members 11 and 12, a. horizontal cross shaft 22 is rotatably journalled in bearings 23 respectively supported from the opposite depending side portions 16a of the platform 16. Also, if desired, intermediate bearings 24 for the shaft 22 may depend from and be secured to the under surface of the platform 16 as will be best seen in Fig. 2.

The upper ends of the side rails 12a of the upper support section carry brackets or bearings26 which'are rotat- For the purpose of simultaneously raising or lowering the respective extensible members 11 and 12, suitable operatively interconnected jack screws are provided. A pair of such screws 27 and 28 is carried by the upper section 11 1 of the ladder, such screws being supported on ladder section 11a for free rotation but in fixed axial positions. Inasmuch as both of these screws are mounted in identical fashion it will sufiice to describe in detail the means exemplified for so supporting but one of them, namely, the screw 27.

It will be seen that the screw 27 is threaded through a cooperating threaded member in the form of a nut 29 fixed o'n its corresponding side rail 11b of the lower ladder section and extends thence upwardly parallel to the ladder to have its upper end terminating in a bearing portion which is freely rotatably supported in bearing 31 fixed on the corresponding side rail 11a of the upper ladder section. A radial thrust collar 32 fixed on the threaded shaft 27 beneath the bearing 31 rotatably abuts against the said' bearing to prevent axial displacement of the threaded screw shaft 27. Thus, it will be seen that by rotation of the screw 27 it will be caused to move axially due to its cooperation with the fixed nut 29 on the lower ladder section and will thereby transmit movement through the bearing 31 to the upper ladder section including the side rails 11a. Thus, extension or contraction of the ladder member by relative movement of its aforesaid two sections may be accomplished incident to rotation of the screw 27. It will be noted that the screw 27 is mounted as aforementioned adjacent and parallel to one of the side rails 11a of the upper ladder member while the screw 28 is mounted in similar manner adjacent the other side rail 11a of the upper ladder member and cooperates with a similar nut 29 fixed on the corresponding side rail 11b of the lower ladder section.

The slidably interconnected prop sections 12:: and 12b are actuated by a similar jack screw arrangement to that aforementioned. Same includes the threaded screw shaft 33, the lower end of which is threadedly received in a nut or other threaded means 34 fixedly supported on a cross bar 35' midway between the two side rails 12b of the lower prop section. The upper end of the screw 33 is rotatably supported through a bearing 36 fixedly carried by cross bar 37 midway between the side rails 12a adjacent the upper end thereof. A radial thrust collar 38 fixed on the shaft 33 rotatably abuts against the under surface of the bearing 36 to prevent axial displacement of the shaft 33 relative to the bearing 36 and upperprop section 12a. It will be seen that the disposition of the several screws 27, 28 and 33 is such that all extend radially to the axis of the shaft 22 and are swingable with their respective members 11 and 12 about the axis of said shaft.

In order to interconnect the said screws 27, 28 and 33 for simultaneous coordinated actuation, there are provided suitably disposed gear means exemplified by the bevel gears 39, 40 and 41, respectively, keyed on the shaft 22. These gears 39, 40- and' 41, respectively, mesh with bevel gears 42, 43 and 44 keyed or otherwise fixed on the upper ends of the jack screws 27, 33 and 28 respectively. It will thus be-seen that the several jack screws are all inter-v connected through the aforesaid shaft 22 and gearing in such manner that rotation of any one of said screws or said shaft will result in simultaneous equal rotation of all of the screws or screw shafts. Thus, if the threads on the respective screws are of equal pitch, as will be the case in the preferred embodiment, the ladder member and the prop member will be caused to extend or contract simultaneously and to equal extents. Incidentally, in the particular arrangement illustrated, it will be noted that the gearing is, so disposed that the two shafts 27 and 33 will rotate in an opposi e di ecti n from he haft .8- T r 4 fore, the shafts 27 and 33 in the specific arrangement illustrated must be of opposite thread than the shaft 28. However, this is by no means essential considering the invention from its broader aspects.

With the foregoing interconnection between the several threaded shafts 27, 28, 33 and the cross shaft 22, it will be readily apparent that any one of them may be rotated by suitable means and from various convenient locations in order to raise and lower the ladder as desired. For instance, the ladder may be readily raised and lowered by an operator mounted on the upper portion of the ladder by means of a hand crank 46 keyed on the outer end of the shaft 22. This is of considerable advantage inasmuch as it will enable a workman to adjust the height of the ladder without dismounting therefrom.

Also, in order to adapt the ladder for easy raising and lowering at a location adjacent its base, suitable means may be provided for imparting rotation from any one of the said jack screws. One suitable form of such means is shown as comprising a hand crank 47 rotatably supported by a gear box 48 fixed on one of the side rails of the, lower ladder section 11b. The arrangement is such that the crank transmits rotation to gearing within the gear box 48 and such gear box in turn is operatively connected to and rotates a tubular shaft or sleeve 49 which is rotatably supported in a bearing 50 on one of the side rails 11b. The upper end of the tubular sleeve 49 freely slidably receives the jack screw 27 but is slidably keyed thereto as at 51, the key 51 working in a keyway 52 in the screw 27 to impart rotation to the screw 27 while permitting a relative telescoping action between the screw and its cooperating sleeve 49. Such rotation of the screw 27 as transmitted from the crank through the sleeve 49 will result in similar rotation of the shaft 22 and the remaining jack screws 28 and 33 with resultant raising or lowering of the ladder in its entirety.

By comparison of Figs. 1 and 3 of the drawings it will be readily apparent that raising or lowering of the ladder will result in angular movement between the members 11 and 12, it being apparent, for instance, that the angle between these members is less when the ladder is raised, as in Fig. 1, than when it is lowered, as in Fig. 3. In order to faciltate such angular movement while affording a steady support for the base of the ladder, the respective lower ends of the members 11b, 11b, and 12b, 121) may be provided with supporting feet 110 and 120, respectively, which are pivotally connected as at 11d and 12d to the respective side rails 11b, 12b for movement about axes parallel to the shaft 22.

Moreover, it will be desirable to provide some linkage or interconnecting means between the lower ends of the ladder members 11 and 12 which will prevent inadvertent spreading apart of the lower ends of these members with resultant collapse of the ladder, while avoiding interference with the angular movement above mentioned between the members 11 and 12. To this end the preferred form of linkage consists of a toggle linkage, the two links 52 and 53 of which have their relatively remote ends pivotally connected to the lower ends of spread the ladder members 11 and 12 apart to place the ladder in use. However, by displacing the knee of the toggle linkage upwardly the hook or lock 56 will be disengaged and the ladder members 11 maybe folded together about the axis of the shaft 22 as shown in Fig. 5 for transport or for storage, all in usual manner.

In this application I have shown and described only the preferred embodiment of the invention simply by way of illustration of the preferred mode of carrying out the invention. However, I recognize that my invention is capable of other and different embodiments and that its several details may be modified in various ways, all without departing from my invention as defined in the accompanying claims. Accordingly, the drawings and description herein are to be construed as merely illustrative in nature and not as restrictive.

Having thus described my invention, I claim:

1. An extensible stepladder comprising an extensible ladder member and an extensible prop member, said ladder member and said prop member each comprising upper and lower linearly slidably interconnected sections, a horizontal shaft rotatably supported at the upper end of one of said upper sections, the other upper section being pivotally connected at its upper end to said first upper section for swinging movement about the axis of said shaft, a jack screw rotatably journalled and axially fixed on each said upper section, intermeshing gearing on said shaft and each of said screws operative to cause rotation together of said shaft and said screws, a nut fixed on each said lower section in threaded engagement with a screw of its respective upper section to cause simultaneous relative sliding movement between the sections of said members incident to rotation of said screws, and means for rotating said shaft.

2. The combination of claim 1, wherein said shaft rotating means comprises a sleeve slidably receiving and keyed to one of said jack screws, means supporting said sleeve for rotation and against axial movement on the lower section of its respective member, and means associated with said sleeve for manually rotating same.

3. The combination of claim 2, in which said rotating means comprises a hand crank rotatable on said last mentioned lower section, and gear means for transmitting rotation from the crank to said sleeve.

4. The combination of claim 1, wherein said rotating means comprises a hand crank fixed on said shaft.

5. An extensible stepladder comprising a pair of individually extensible bipartite members, each comprising upper and lower slidably interconnected sections, a rotatable pivot shaft pivotally connecting said upper sections for relatively swinging movement, a threaded jack screw shaft rotatably journalled and axially fixed on each said upper section radially to the axis of said pivot shaft, intermeshing gearing on said pivot shaft and each of said jack screw shafts for causing simultaneous rotation of said shafts in any of the relative angular positions of said upper sections, threaded means fixed on each of said lower sections, each said means operatively engaging a jack screw shaft of its respective member to extend or retract said member incident to rotation of said shafts, and means associated with one of said shafts for rotating same.

6. The combination of claim 5 including supporting feet pivotally mounted at the lower ends of the respective lower sections, for movement about axes parallel to said pivot shaft.

7. The combination of claim 6, including a link extending between and interconnecting the lower ends of the said lower sections against relative spreading, said link being pivotally interconnected to the respective lower ends coincidentally with the pivotal mountings of the respective supporting feet, to avoid interference with relative angular movement between the members incident to the extension and retraction.

8. The combination of claim 7 in which said link comprises a foldable toggle linkage.

9. An extension ladder comprising relatively linearly slidably associated upper and lower ladder sections, inter engaging threaded means carried by the respective sections for relative rotation about an axis parallel to the relative sliding movement of said sections, said threaded means being axially immovable on their respective sections, and means on one member for rotating its respective threaded means to extend and retract the respective sections, in combination with a cross-shaft rotatably journalled on said upper section, an extensible prop having an upper prop section swingably supported on said shaft, and a lower prop section slidably supported on said upper prop section, interengaging threaded means respectively carried by the last mentioned prop sections forextending and retracting said prop, and gear means on said shaft and on the said threaded means of each of said upper sections interconnecting said shaft and said last mentioned threaded means for rotation together.

References Cited in the file of this patent UNITED STATES PATENTS 79,079 Pierce et a1. June 23, 1868 1,731,611 Clark Oct. 15, 1929 1,901,726 Bonnet Mar. 14 1933 2,376,529 Yarmolowich May 22, 1945 FOREIGN PATENTS 2,246 Great Britain 1862 968,627 France Apr. 26, 1950

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